Method and apparatus for attaching a sensor assembly in a control unit

ABSTRACT

A control unit for a safety restraint device includes a main printed circuit board that supports lateral and vertical acceleration sensors and an auxiliary printed circuit board that supports rollover sensors. The main and auxiliary printed circuit boards are spaced apart from and are positioned in an overlapping relationship to each other within a housing. A pin connection provides electrical connection between the main and auxiliary printed circuit boards to permit signal transfers between the main and auxiliary printed circuit boards. A common fastener is used to connect both the main and auxiliary printed circuit boards to the housing. A cover is used to enclose the main and auxiliary printed circuit boards within the housing. The fastener extends through the cover, through both the main and auxiliary printed circuit boards, and finally into the housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application is a DIV of and claims priority to U.S. application Ser.No. 10/445,526 filed on May 27, 2003 now U.S. Pat. No. 6,913,472, whichclaims priority to U.S. Provisional Application No. 60/392,146, whichwas filed on Jun. 28, 2002.

BACKGROUND OF THE INVENTION

This invention relates to a method and apparatus for attaching a sensorassembly within a control unit that is used to deploy a safety restraintdevice.

Electronic control units for deploying safety restraint devices includea plurality of sensors and a printed circuit board, which interact witheach other to control deployment of the safety restraint device underappropriate vehicle crash conditions. Traditionally, a single printedcircuit board is used to support all of the sensors. Thus, the lateraland vertical acceleration sensors as well as the rollover sensors areall mounted to the same circuit board.

This mounting configuration has several disadvantages. First, the sizeof the circuit board must be large enough to accommodate all of thesensors, in addition to their associated electronics. This takes up asignificant amount of packaging space. Another disadvantage is that thismounting configuration has a tendency to resonate at lower frequencies.This resonation can adversely affect sensor signals, resulting inmeasurement and signal conversion inaccuracies.

Thus, it is desirable to have a control unit and sensor assembly thatallows the size of the printed circuit board to be decreased to providea more compact unit, and which further eliminates inaccuracies caused byvibrations, as well as overcoming the other above mentioned deficiencieswith the prior art.

SUMMARY OF THE INVENTION

A control unit for a safety restraint device includes a main printedcircuit board that supports a first sensor and a secondary or auxiliaryprinted circuit board that supports a second sensor. The main andauxiliary printed circuit boards are spaced apart from and arepositioned in an overlapping relationship to each other within ahousing. A common attachment member is used to connect both the main andauxiliary printed circuit boards to the housing.

In one disclosed embodiment, the control unit and sensor assembly for asafety restraint device includes a housing, non-coplanar first andsecond printed circuit boards supported within the housing, and afastener that attaches both printed circuit boards to the housing. Arigid tubular member is positioned between the first and second printedcircuit boards. The rigid tubular member is aligned with first andsecond openings formed within the first and second printed circuitboards, respectively. The fastener extends through the first and secondopenings, through the rigid tubular member, and has a distal end that isembedded within a wall of the housing.

In one disclosed embodiment, the first printed circuit board comprises amain or primary printed circuit board and the second printed boardcomprises an auxiliary or secondary printed circuit board. Accelerationsensors that measure lateral and/or vertical vehicle accelerations arepreferably mounted on the main printed circuit board. A rollover sensorassembly, which measures a vehicle angular rate, is separated from theother sensors and is mounted to the auxiliary printed circuit board.

In one disclosed embodiment, more than one fastener is used to attachthe printed circuit boards to the housing. In this embodiment, eachfastener is spaced apart from one another and each fastener extendsthrough both the first and second printed circuit boards. Distal ends ofthe fasteners are embedded in a wall of the housing.

The subject method and apparatus provides a more compact control unitand sensor assembly for deploying a safety restraint device. These andother features of the present invention can be best understood from thefollowing specifications and drawings, the following of which is a briefdescription.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a schematic view of a vehicle system incorporating the subjectinvention.

FIG. 2 is a cross-sectional view, partially cut away, of a vehiclesystem control unit incorporating the subject invention.

FIG. 3 is a cross-sectional view taken along line 3—3 of FIG. 2.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

A control unit and sensor assembly, shown generally at 10 in FIG. 1,measures and analyzes multiple vehicle characteristics to determinewhether conditions are appropriate for deploying a safety restraintdevice 12. The control unit and sensor assembly 10 includes plurality ofsensors 14 that transmit signals to an electronic control and processingunit (ECU) 16. The sensors 14 and ECU 16 are enclosed within a housing18, which is mounted to a vehicle structure 20. The ECU 16 monitors thesensor signal and generates an activation signal 22 when the ECU 16determines that conditions are appropriate to activate the safetyrestraint device 12.

Preferably, the control unit and sensor assembly 10 is mounted near avehicle width centerline. Also, the control unit and sensor assembly 10is preferably positioned as close to a vehicle firewall as possible,such as within the center counsel area in the vehicle.

The control unit and sensor assembly 10 includes a primary or mainprinted circuit board 24 and a secondary or auxiliary printed circuitboard 26. The auxiliary printed circuit board 26 is non-coplanar withthe main printed circuit board 24. As shown in FIG. 2, the auxiliaryprinted circuit board 26 is spaced apart from and positioned in anoverlapping relationship to the main printed circuit board 24. The mainprinted circuit board 24 supports at least one sensor assembly 28, aswell as supporting ECU associated electronics 30. The auxiliary printedcircuit board 26 supports at least one additional sensor assembly 32. Apin connection 34 is used to electronically connect the auxiliaryprinted circuit board 26 to the main printed circuit board 24. Any typeof pin connection 34 known in the art, such as a standard bandolierstandoff, press-fit connection or solder joint, for example, could beused to form this connection.

Preferably, the sensor assembly 28 mounted on the main printed circuitboard 24 includes acceleration sensors that measure lateral and/orlongitudinal vehicle accelerations, while the additional sensor assembly32 supported on the auxiliary printed circuit board 26 includes arollover sensor that measures an angular rollover or turning rate. Itshould be understood that each of the sensor assemblies 28, 32 could becomprised of a single sensor or could be comprised of multiple sensors.Also, while it is preferable to separate the lateral and longitudinalacceleration sensors from the rollover sensors, the auxiliary printedcircuit board 26 could be configured to support lateral and verticalacceleration sensors in addition to, or in place of, the rolloversensors.

Further, any associated sensor electronics 36 for the additional sensorassembly 32, are preferably mounted on the auxiliary printed circuitboard 26. The associated sensor electronics 36 or any additional sensorsor sensor components 38 used to form the additional sensor assembly 32can be positioned on an upper surface 40 or on a lower surface 42 of theauxiliary printed circuit board 26, depending upon packagingconstraints.

At least one attachment member 44 is used to secure both the main 24 andauxiliary 26 printed circuit boards to the housing 18. The attachmentmember 44 includes a body portion 46 that extends through both the main24 and auxiliary 26 printed circuit boards. A distal end 48 of the bodyportion 46 extends into or is embedded within a wall 50 of the housing18.

A rigid tubular standoff or spacer 52 is positioned between the main 24and auxiliary 26 printed circuit boards. The spacer 52 includes a bore54 through which the attachment member 44 is inserted. A cover 56 isused to enclose the main 24 and auxiliary 26 printed circuit boardswithin the housing 18. The cover also provides a protected environmentfor the sensors 28, 32 and electronics 30, 36.

A first opening 58 is formed within the cover 56, a second opening 60 isformed within the main printed circuit board 24, and a third opening 62is formed within the auxiliary printed circuit board 26. The openings58, 6O, 62 are aligned with one another and with the bore 54 of thespacer 52. The attachment member 44 is inserted through the firstopening 58, through the second opening 60, through the bore 54, throughthe third opening 62 and into the housing wall 50. Thus, the sameattachment member 44 is inserted through the cover 56, main printedcircuit board 24, the spacer 52, and the auxiliary printed circuit board26.

Preferably, the housing 18 includes a ledge 64 against which theauxiliary printed circuit board 26 abuts. The third opening 62 in theauxiliary printed circuit board 26 is aligned with the ledge 64 suchthat the attachment member 44 can be inserted through the opening 62 andinto the housing wall 50.

Preferably, the attachment member 44 comprises at least two fasteners 44a and 44 b as shown in FIG. 3. The fasteners 44 a, 44 b are preferablythreaded fasteners that have distal ends 48 a, 48 b that are threadedinto gripping engagement with the housing wall 50. The fasteners 44 a,44 b include body portions 46 a, 46 b that extend through the firstopenings 58 a, 58 b, through the second openings 60 a, 60 b, through thebores 54 a, 54 b of the rigid spacers 52 a, 52 b, through the thirdopenings 62 a, 62 b, and into the housing wall 50. Thus, both fasteners44 a, 44 b are inserted through the cover 56, main printed circuit board24, the spacer 52, and the auxiliary printed circuit board 26 to providea secure and rigid attachment of the boards 24, 26 to the housing 18.

While at least two fasteners 44 a, 44 b are preferred, it should beunderstood that only one fastener 44 may be required. The determinationof whether the single fastener mounting configuration can be used isbased on system requirements and the specific module configuration.

This packaging and mounting configuration for the control unit andsensor assembly 10 provides several advantages. The attachment members44 a, 44 b provide solid attachment to the housing 18, which improvessignal transfer to the rollover sensors in the additional sensorassembly 32. Further, because the rollover sensors 32 are mounted on theauxiliary printed circuit board 26, the rollover sensors 32 are isolatedfrom dynamic resonating input generated by the main printed circuitboard 24. Also, the configuration minimizes the main printed circuitboard space requirements for adding the rollover feature. Thus,additional space is provided on the main printed circuit board 24 forother electrical components.

Another advantage is that the size of the main printed circuit board 24is standardized for different sensor configurations. The rolloverfunction is an optional content feature, and thus the rollover sensorand associated electronics are not always required. The subjectinvention provides a compact unit size for modules with and without therollover sensor feature by providing the same main printed circuit boardsize for both applications.

Another benefit is that the control unit and sensor assembly 10 isserviceable because the fasteners 44 a, 44 b can be easily removed andre-installed. The length of the fasteners 44 a, 44 b can vary dependingon the size of the control unit and sensor assembly 10, however, thefasteners 44 a, 44 b must be long enough to extend through the cover 56,main printed circuit board 24, spacer 52, auxiliary printed circuitboard 26, and into the housing wall 50 to form a solid attachment. Theuse of this type of long fastener 44 a, 44 b eliminates the need foradditional fasteners to secure the cover to the housing 18, etc. Thus,one fastening operation is used to secure multiple components to thehousing 18. Further, this mounting configuration is flexible such thatdifferent auxiliary 26 and main 24 printed circuit board shapes andsizes are easily accommodated.

Although a preferred embodiment of this invention has been disclosed, aworker of ordinary skill in this art would recognize that certainmodifications would come within the scope of this invention. For thatreason, the following claims should be studied to determine the truescope and content of this invention.

1. A sensor assembly for a safety restraint control unit comprising: amain printed circuit board; a first sensor supported on said mainprinted circuit board; an auxiliary printed circuit board electricallyconnected to said main printed circuit board wherein said auxiliaryprinted circuit board is non-coplanar with said main printed circuitboard; a second sensor supported on said auxiliary printed circuitboard; and at least one attachment member that attaches both said mainand auxiliary printed circuit boards to a housing.
 2. The sensorassembly set forth in claim 1 wherein said auxiliary printed circuitboard is spaced apart from and positioned in an overlapping relationshipto said main printed circuit board.
 3. The sensor assembly set forth inclaim 1 wherein said attachment member comprises at least one fastenerhaving a body portion that concurrently secures said main and auxiliaryprinted circuit boards to said housing.
 4. The sensor assembly set forthin claim 1 wherein said first sensor comprises at least one accelerationsensor for measuring a vehicle acceleration and wherein said secondsensor comprises at least one rollover sensor for measuring a vehicleangular roll rate.
 5. The sensor assembly set forth in claim 1 whereinthe housing substantially surrounds said main and auxiliary printedcircuit boards.
 6. The sensor assembly set forth in claim 1 wherein saidattachment member extends through said main and auxiliary printedcircuit boards and includes a distal end that is at least partiallyembedded within the housing.
 7. The sensor assembly set forth in claim 1wherein said main and auxiliary printed circuit boards comprise anelectronic control unit that generates an activation signal for a safetyrestraint device based on data received from said first and secondsensors.
 8. A control unit and sensor assembly for a safety restraintdevice comprising: a housing; a first printed circuit board supported bysaid housing; a second printed circuit board supported by said housing,said second printed circuit board being spaced apart from and positionedin an overlapping relationship to said first circuit board; at least onesensor mounted on said second printed circuit board and electricallyconnected to said first printed circuit board; and at least oneattachment member that simultaneously secures said first and secondprinted circuit boards directly to said housing.
 9. The assembly setforth in claim 8 wherein said at least one sensor comprises a rolloversensor that measures a vehicle angular rate.
 10. The assembly set forthin claim 9 including at least one acceleration sensor mounted on saidfirst circuit board.
 11. The assembly set forth in claim 8 wherein saidfirst circuit board includes a first opening, said second circuit boardincludes a second opening, and said housing includes a third opening,said first, second, and third openings being positioned in alignmentwith each other to receive said attachment member.
 12. The assembly setforth in claim 11 including a rigid tubular support positioned betweensaid first and second printed circuit boards and in alignment with saidfirst, second, and third openings.
 13. The assembly set forth in claim12 including a cover attached to said housing to enclose said first andsecond printed circuit boards within said housing.
 14. The assembly setforth in claim 11 wherein said first printed circuit board comprises aprimary printed circuit board and said second printed circuit boardcomprises an auxiliary printed circuit board electrically connected tosaid primary printed circuit board with a plurality of pins.
 15. Theassembly as set forth in claim 8 wherein said attachment member extendsthrough said first and second printed circuit boards to a distal endthat is at least partially embedded within said housing.
 16. Theassembly set forth in claim 8 wherein said first printed circuit boardincludes a first opening and said second printed circuit board includesa second opening with said at least one attachment member extendingthrough said first and second openings.
 17. A method for assembling asafety restraint device control unit and sensor assembly comprising thesteps of: (a) positioning main and auxiliary printed circuit boards inan overlapping relationship to each other; and (b) simultaneouslyfastening the main and auxiliary printed circuit boards to a sensorhousing with a common fastener.
 18. The method set forth in claim 17including the steps of mounting at least one rollover sensor to theauxiliary printed circuit board for generating a vehicle angular ratesignal, mounting at least one acceleration sensor to the main printedcircuit board for generating a vehicle acceleration signal, andelectrically connecting the auxiliary printed circuit board to the mainprinted circuit board.
 19. The method set forth in claim 17 includingthe step of inserting at least one attachment member through the mainand auxiliary printed circuit boards to secure the main and auxiliaryprinted circuit boards to the sensor housing.
 20. The method set forthin claim 17 including the steps of aligning a first hole in the mainprinted circuit board with a second hole in the auxiliary printedcircuit board, and inserting the common fastener through the first andsecond holes to secure the main and auxiliary printed circuit boards tothe sensor housing with a distal end of the common fastener beingembedded within a housing wall of the sensor housing.